Polyethylene in Space Jonathon Ball, Kirk Norasak Goals For the Summer Develop an irradiation setup to imitate “space” conditions. To test mechanical properties of UHMWPE irradiated in “space” conditions. To improve the Orthopod wear testing program. To wear test the proton irradiated PE at Earth STP. Questions to Address • What are the radiation conditions in space? • What are conditions at different points in space? • Why is polyethylene used in space? • What are the uses of polyethylene in space? • What other polymers are used in space? • Polymers Irradiated in a Vacuum vs. Air • Ideas for system setup to imitate polyethylene in space conditions. • Timeline for wear testing of polyethylene samples proton-irradiated in STP of earth. What are the radiation conditions in space? galactic cosmic rays solar particle events ◦Includes protons and highly charged nuclei. ◦Includes protons from Solar Flares, and large mass releases from the sun. 87% of the particles of the GCR are protons, 12% are helium nuclei and 1% are particles heavier than helium Characteristics of space radiation Characteristic SPE GCR proton energy range (MeV) up to several 100 up to several 1000 HZE energy range (MeV/nucleon) no significant contribution up to several 1000 OVERVIEW OF NASA’S SPACE RADIATION RESEARCH PROGRAM Walter Schimmerling National Aeronautics and Space Administration, Washington, DC What are conditions at different points in space? International Space Station- (-157)C - 121C 0mbar pressure Moon- (-233)C - 123C 0mbar pressure Mars- (-153)C - 20C 7.5mbar pressure Reentry to the atmosphere- ~8000K Why is polyethylene used in space? • Readily available. • The high hydrogen content allows this polymer to block radiation neutrons. • Can be easily made into a composite Ex.(Boron Nitride, and Carbon nanotubes.) to improve properties such as Young's Modulus. What are the uses of polyethylene in space? • The PE is used in the crew quarters on the International Space Station. Provided 22% reduction in radiation exposure while in the space station. • Used in the fibers and fabrics of Space suits. • PE based material RXF1 was developed to possibly build a plastic space ship to replace the Al outer shell. 3X stronger and 2.6X lighter than Al. 50% better SPE shielding and 15% better Cosmic ray shielding. Increased shielding would be necessary for a mission to Mars which is expected to last at least 30 months. What other polymers are used in space? Mylar (PET)- Has radiation resistance Electrical insulator Used to make Solar Sails Kapton - Temp range -273 to 400 C Used for wire coating Used as an insulator in UH Vac environment Neoprene- Insulation (Wet suits) to regulate body temperature. PTFE (Teflon) – Outer protection on the space suit. Polymers Irradiated in a Vacuum vs. Air Vacuum samples that are irradiated show improved mechanical properties. Under the vacuum PTFE has shown to reduce toxic components such as HF. UHMWPE in pre-irradiation vacuum removed oxygen in the system, thus leaving more free radicals to form crosslinks. System setup to imitate polyethylene in space conditions. Vacuum package the PE and immerse it into a liquid Nitrogen storage device. After that, place the setup into the radiation testing area. Questions still to be answered for the setup: ◦What is the pressure of the polyethylene while vacuum packaged? ◦What is the radiation shielding coefficient of the packaging material? ◦How to quantify the temperature of the PE immersed in the LN? ◦Does the LN have a shielding effect? ◦Is the effects due to the lack of Oxygen or the pressure the Vacuum presents? Timeline of Pin-on-Disk wear testing for polyethylene that was proton-irradiated at Earth's STP 2 weeks- machining time on pins, receiving new SS buttons, new circle programming Begin Testing June 27 ◦ 2 days per 10 km Every MWF begin new runs of 10km Run samples for 40km stopping every 10km to determine wear ratios. Focus on 0Gy and 35Gy samples of 1020 PE and 1020E PE for a total of 4 sample sets. ◦ Using the developed schedule, testing on the 4 different sets would be completed August 3. References (1) Archodoulaki, V. -.; Koch, T.; Rodriguez, A.; Seidler, S. Influence of Different Sterilization Procedures on the Morphological Parameters and Mechanical Properties of Ultra-High-Molecular-Weight Polyethylene. J Appl Polym Sci 2011, 120, 1875-1884. (2) Banford, H. M.; Yufen, W.; Tedford, D. J.; Given, M. J. The dielectric response of polyimide to combined radiation, vacuum and thermal aging. IEEE 1995 Annual Report.Conference on Electrical Insulation and Dielectric Phenomena (Cat.No.95CH35842) 1995, 239; 239-242; 242. (3) Brichard, B.; Ooms, H.; Starckx, J.; Fernandez, A. F.; van Uffelen, M.; Berghmans, F. SCK-CEN gamma irradiation facilities for radiation testing in high-vacuum conditions. Proceedings of the 7th European Conference on Radiation and its Effects on Components and Systems - RADECS 2003 (IEEE Cat.No.03TH8776) 2004, 513; 513-515; 515. (4) Burroughs, B. R.; Blanchet, T. A. The effect of pre-irradiation vacuum storage on the oxidation and wear of radiation sterilized UHMWPE. Wear 2006, 261, 1277-1284. (5) Chiggiato, P.; Kersevan, R. Synchrotron radiation-induced desorption from a NEG-coated vacuum chamber. Vacuum 2001, 60, 67-72. (6) Guetersloh, S.; Zeitlin, C.; Heilbronn, L.; Miller, J.; Komiyama, T.; Fukumura, A.; Iwata, Y.; Murakami, T.; Bhattacharya, M. Polyethylene as a radiation shielding standard in simulated cosmic-ray environments. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2006, 252, 319-332. (7) Huot, J. C.; Van Citters, D. W.; Currier, J. H.; Collier, J. P. The effect of radiation dose on the tensile and impact toughness of highly cross-linked and remelted ultrahigh-molecular weight polyethylenes. J. Biomed. Mater. Res. 2011, 97B, 327-333. References cont. (8) Korenev, S. Method of radiation degradation of PTFE under vacuum conditions. Radiat. Phys. Chem. 2004, 71, 523-525. (9) Korenev, S. Method of radiation degradation of PTFE under vacuum conditions. Radiat. Phys. Chem. 2004, 71, 523-525. (10) Premnath,V.; Harris, W. H.; Jasty, M.; Merrill, E. W. Gamma sterilization of UHMWPE articular implants: An analysis of the oxidation problem. Biomaterials 1996, 17, 1741-1753. (11) Sarcinelli, L.; Valenza, A.; Spadaro, G. Inverse response of polypropylene to gamma radiation under vacuum. Polymer 1997, 38, 2307-2313. (12) Schimmerling,W. Overview of NASA's space radiation research program. Gravit Space Biol Bull 2003, 16, 510. (13) Shavers, M. R.; Zapp, N.; Barber, R. E.; Wilson, J. W.; Qualls, G.; Toupes, L.; Ramsey, S.;Vinci,V.; Smith, G.; Cucinotta, F. A. Implementation of ALARA radiation protection on the ISS through polyethylene shielding augmentation of the Service Module Crew Quarters. Advances in Space Research 2004, 34, 1333-1337. (14) Stephens, C. P.; Benson, R. S.; Esther Martinez-Pardo, M.; Barker, E. D.; Walker, J. B.; Stephens,T. P. The effect of dose rate on the crystalline lamellar thickness distribution in gamma-radiation of UHMWPE. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2005, 236, 540-545. (15) Zhong,W. H.; Miller, J. In In Reactive nano-epoxy matrix and the UHMWPE fiber composites for cosmic radiation shielding; International Conference on Smart Materials and Nanotechnology in Engineering, July 1, 2007 July 4; SPIE: Harbin, China, 2007;Vol. 6423, pp SPIE; Harbin Institute of Technology, China. (16) Zhong,W. H.; Sui, G.; Jana, S.; Miller, J. Cosmic radiation shielding tests for UHMWPE fiber/nano-epoxy composites. Composites Sci.Technol. 2009, 69, 2093-7. References cont. (17) Ask A Scientist. http://earthobservatory.nasa.gov/Features/AskScientist/askscientist_3.php#q27 (accessed June 6, 2011). (18) What is the temperature on the Moon? http://lunarscience.nasa.gov/kids/moon_temperature (accessed June 6, 2011). (19) Mars Facts. http://quest.nasa.gov/aero/planetary/mars.html (accessed June 6, 2011). (20) Barry, P. L. Plastic Spaceships. http://science.nasa.gov/science-news/science-atnasa/2005/25aug_plasticspaceships/ (accessed June 6, 2011). (21) Pline, A. Exploration: Moon, Mars, and Beyond. http://www.nasa.gov/mission_pages/exploration/mmb/index.html (accessed June 6, 2011). (22) Price, S.; Phillips, T.; Knier, G. Staying Cool on the ISS. http://science.nasa.gov/science-news/science-atnasa/2001/ast21mar_1/ (accessed June 6, 2011).